The most famous Canal Zone stamp was the four cent stamp (Scott #157, error stamp #157a), issued on October 12, 1962, for the opening of the Thatcher Ferry Bridge (now the Bridge of the Americas), the first elevated bridge connecting the two sides of the Canal.
The Post Office Department’s action concerning the Dag Hammarskjold error cannot be repeated today because of a law resulting from a case instigated by H.E. Harris. Harris, one of the promoters of stamp collecting in America and founder of the H.E. Harris Co., obtained a sheet of 1962 Canal Zone stamps containing errors (One pane of fifty stamps was released without the silver ink used to depict the Bridge).
The stamps were issued to commemorate the Thatcher Ferry Bridge, but on the error stamps the bridge itself had been omitted. One pane of fifty stamps was released without the silver ink used to depict the Bridge. The Canal Zone, Upon learning of this, planned to print millions of stamps bearing the same error to destroy the value of the errors, just as the United States did with the Dag Hammarskjold error.
In this case, however, Harris stopped them with court action. The law that emerged from this famous case came too late to affect the Dag Hammarskjold error of 1962, but it prohibited to Canal Zone Post Office from printing more error stamps of the Thatcher Ferry Bridge Commemorative. And this law still applies to the United States and her possessions such as the Canal Zone.